auto-clang-format is an Emacs package that defines a minor mode
(auto-clang-format-mode) that runs clang-format-buffer before the buffer is
saved to its file. Exception: clang-format-buffer will not be run if a style
hasn't been selected, i.e. if there is no ".clang-format" file in the directory
tree and clang-format-style hasn't been set to an explicit style. If the
minor mode will call clang-format-buffer the mode line will include the
indicator "ACF", otherwise "!ACF".
auto-clang-format depends on the clang-format package.
To load and enable auto-clang-format-mode unconditionally, put something like
this in your Emacs configuration:
(require 'auto-clang-format)
(add-hook 'c++-mode-hook 'auto-clang-format-mode)